American officials have cause to worry there may be more al Qaeda-trained young men in Yemen planning to bring down American jets.

Umar Farouk Abdulmutallab, charged with the attempted Christmas Day bombing of Northwest Airlines flight 253, told FBI agents there were more just like him in Yemen who would strike soon.

And in a tape released four days before the attempted destruction of the Detroit-bound Northwest plane, the leader of al Qaeda in Yemen boasted of what was planned for Americans, saying, "We are carrying a bomb to hit the enemies of God."

Yemen has become a principal al Qaeda training ground and the accused suicide bomber told the FBI he was trained for more than a month in Yemen, given 80 grams of a high explosive cleverly sewn into his underpants, undetected by standard security screening.

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"They know that this is a weakness and an Achilles' heel in our airport security system," said ABC News consultant and former counterterrorism czar Richard Clarke.

Law enforcement authorities say tragedy was averted only because the bomb's detonator did not work.

"I think it's very clear it came very, very close," said Rep. Pete Hoekstra, ranking minority member of the House Intelligence Committee. "The explosive device went off, it became an incendiary device instead of an explosive device, which is probably what saved that airplane."

On Sunday, in its first communication since the failed Northwest Airline bombing, Al Qaeda in Yemen released a written statement about the December 17 air strike in Yemen. The statement called on "the people of the Arabian peninsula" to attack American military installations, ships and "spying embassies." The U.S. Embassy in Yemen was attacked by Al Qaeda-affiliated terrorists in September 2008, and the U.S.S. Cole, a U.S. Navy destroyer, was hit by Al Qaeda in 2000.

Abdulmutallab's Life of Privilege

Abdulmutallab led a life of privilege as the son of a prominent Nigerian banker.

He lived in an upscale neighborhood in London, attended top boarding schools and a London college.

Michael Rimmer, one of his former high school teachers, called him "a model student, very keen, very enthusiastic."

"He was a very nice, friendly person," said Efemena Mokedi, a former classmate. "He was a person who did a lot of good things."

In e-mails sent over the last six years, and obtained by ABC News, Abdulmutallab worried whether his religion would allow him to attend a high school prom, worried about low college SAT test scores, expressed opposition to the war in Iraq and Afghanistan, and then prior to breaking with his parents, questioned whether it was okay to lie to deceive the enemy.

Explained Clarke, "The kind of person, who's being radicalized increasingly in the U.S. and in Europe, are people who are sons of the middle class, the upper middle class, sons of well educated families, people who have radicalized at long distance over the Internet."

The suspect's father was so concerned about his son's radicalization he actually alerted the U.S. embassy in Nigeria that his son could be a threat to America.

Abdulmutallab was put on a terror watch list, along with 550,000 others, but he was not put on the no-fly list and his U.S. visa, which he obtained a year and a half ago, was not revoked. He used the visa to board the flight to Detroit Christmas morning.